Build/Test Tools: Use input added in [58274] in the 6.2 branch.

This was missed in [58301].

See #59416, #61213.

git-svn-id: https://develop.svn.wordpress.org/branches/6.2@58349 602fd350-edb4-49c9-b593-d223f7449a82

.github/workflows/test-build-processes.yml

@@ -50,9 +50,15 @@ jobs:
       matrix:
         os: [ ubuntu-latest, windows-latest ]
         directory: [ 'src', 'build' ]
+        include:
+          # Only prepare artifacts once.
+          - os: ubuntu-latest
+            directory: 'build'
+            prepare-playground: ${{ github.event_name == 'pull_request' && true || '' }}
     with:
       os: ${{ matrix.os }}
       directory: ${{ matrix.directory }}
+      prepare-playground: ${{ matrix.prepare-playground && matrix.prepare-playground || false }}
       test-emoji: false
 
   # Tests the WordPress Core build process on MacOS.